/**
 * @author felixturner / http://airtight.cc/
 *
 * RGB Shift Shader
 * Shifts red and blue channels from center in opposite directions
 * Ported from http://kriss.cx/tom/2009/05/rgb-shift/
 * by Tom Butterworth / http://kriss.cx/tom/
 *
 * amount: shift distance (1 is width of input)
 * angle: shift angle in radians
 */

var DigitalGlitch = {
  uniforms: {
    tDiffuse: { value: null }, //diffuse texture
    tDisp: { value: null }, //displacement texture for digital glitch squares
    byp: { value: 0 }, //apply the glitch ?
    amount: { value: 0.08 },
    angle: { value: 0.02 },
    seed: { value: 0.02 },
    seed_x: { value: 0.02 }, //-1,1
    seed_y: { value: 0.02 }, //-1,1
    distortion_x: { value: 0.5 },
    distortion_y: { value: 0.6 },
    col_s: { value: 0.05 },
  },

  vertexShader: [
    'varying vec2 vUv;',
    'void main() {',
    'vUv = uv;',
    'gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );',
    '}',
  ].join('\n'),

  fragmentShader: [
    'uniform int byp;', //should we apply the glitch ?
    'uniform sampler2D tDiffuse;',
    'uniform sampler2D tDisp;',
    'uniform float amount;',
    'uniform float angle;',
    'uniform float seed;',
    'uniform float seed_x;',
    'uniform float seed_y;',
    'uniform float distortion_x;',
    'uniform float distortion_y;',
    'uniform float col_s;',
    'varying vec2 vUv;',
    'float rand(vec2 co){',
    'return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);',
    '}',
    'void main() {',
    'if(byp<1) {',
    'vec2 p = vUv;',
    'float xs = floor(gl_FragCoord.x / 0.5);',
    'float ys = floor(gl_FragCoord.y / 0.5);',
    //based on staffantans glitch shader for unity https://github.com/staffantan/unityglitch
    'vec4 normal = texture2D (tDisp, p*seed*seed);',
    'if(p.y<distortion_x+col_s && p.y>distortion_x-col_s*seed) {',
    'if(seed_x>0.){',
    'p.y = 1. - (p.y + distortion_y);',
    '}',
    'else {',
    'p.y = distortion_y;',
    '}',
    '}',
    'if(p.x<distortion_y+col_s && p.x>distortion_y-col_s*seed) {',
    'if(seed_y>0.){',
    'p.x=distortion_x;',
    '}',
    'else {',
    'p.x = 1. - (p.x + distortion_x);',
    '}',
    '}',
    'p.x+=normal.x*seed_x*(seed/5.);',
    'p.y+=normal.y*seed_y*(seed/5.);',
    //base from RGB shift shader
    'vec2 offset = amount * vec2( cos(angle), sin(angle));',
    'vec4 cr = texture2D(tDiffuse, p + offset);',
    'vec4 cga = texture2D(tDiffuse, p);',
    'vec4 cb = texture2D(tDiffuse, p - offset);',
    'gl_FragColor = vec4(cr.r, cga.g, cb.b, cga.a);',
    //add noise
    'vec4 snow = 200.*amount*vec4(rand(vec2(xs * seed,ys * seed*50.))*0.05);',
    'gl_FragColor = gl_FragColor+ snow;',
    '}',
    'else {',
    'gl_FragColor=texture2D (tDiffuse, vUv);',
    '}',
    '}',
  ].join('\n'),
}

export { DigitalGlitch }
